The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing system implementing atomic layer deposition (ALD) and chemical vapor deposition (CVD) may be used to deposit film on a substrate such as a semiconductor wafer. Some types of ALD may involve dosing a processing chamber with a first precursor for a predetermined period to allow the first precursor to adsorb onto the surface of the substrate. After the predetermined period, the process chamber is purged using valves and vacuum pumps. Then, a second precursor may be introduced and/or activation may be performed. Another purge may be performed. Each ALD cycle deposits a thin layer of film. Typically, the ALD cycle is repeated multiple times to achieve a desired film thickness. In contrast, some CVD involves exposing the substrate to first and second precursors at the same time to create the film on the surface of the substrate.
Throughput is an important characteristic of any substrate processing system. Therefore, the amount of time that is needed to deposit the desired thickness of the film is an important metric when evaluating a tool. Additional considerations include downtime that will be required to maintain the tool. As can be appreciated, valve cycle time and maintenance may impact throughput.
Valves may be used to deliver and purge the precursors and purge gas to/from the process chamber. While gate valves or similar active sealing valves may be used for this application, the maximum life cycle of these valves may be reached in an unacceptably short amount of time due to the high cycle count. The valves tend to fail due to the wear of the seal, which is typically made of a polymer material.
Low-conductance, non-sealing throttle valves have also been used. The throttle valves use either a flat metal-on-metal surface or a seal ring type low-conductance position. Over time, process byproduct builds up on the valves, which increases leakage across the throttle valve. Furthermore, the process needs to be stopped frequently to allow valve openings to be cleaned. Both of these throttle valve types struggle to meet high cycle requirements and tool availability demands presented by ALD or CFD applications.